Objective To explore the clinical effect of different doses of alfentanil combined with low-dose propofol in painless colonoscopy in elderly patients.Methods A total of 120 elderly patients undergoing elective painless colonoscopy from January to March 2022,aged 65 to 80 years,gender unlimited,body mass index(BMI)18-28kg/m2,American Society of Anesthesiologists(ASA)grade Ⅰ～Ⅱ.Patients were included in the three groups by random number tables:alfentanyl 5μg/kg(N1),alfentanyl 7.5μg/kg(N2),and alfentanyl 10μg/kg(N3),40 patients in each group.Record the heart rate,mean arterial pressure,and oxygen saturation were recorded before anesthesia(T1),after anesthesia induction(T2),colonoscopy(T3),colonoscopy reaching the ileocecum(T4),and at the end of examination(T5).The success rate of anesthesia sedation,dosage of propofol,sedative induction time,colonoscopy time,sedative recovery time,use of vasoactive drugs and physician satisfaction of the three groups were recorded.The incidence of intraoperative hypoxemia,hypotension,spontaneous ycardia,bradycardia,postoperative nausea and dizziness,and postoperative fatiguesyndrome(POFS)and the occurrence of adverse reactions.Results Compared with T1,the mean arterial pressure in T2-T5 patients decreased significantly(P＜0.05),and the heart rate at T3 increased significantly(P＜0.05)in N1,the total dosage,induction time,induction time,awakening time and vasoactive drug use were decreased in N2 and N3,and the success rate of anesthesia sedation was significantly increased(P＜0.05).Comparing the N2 group,physician satisfaction decreased in the N1 and N3 groups(P＜0.05).The incidence of intraoperative hypotension and postoperative POFS decreased in the N2 and N3 groups(P＜0.05)and in the N1 and N2 groups(P＜0.05).Conclusion Afunentanil 7.5pg/kg compound propofol can be used safely and effectively for painless colonoscopy in elderly patients,and the incidence of adverse reactions is low,which improves the quality of postoperative recovery of patients,and is worthy of clinical promotion and application.